KAVS you are more or less correct in everything except:
then you will pass threw the partially existing Pier D and arriving in T2
It's the partially existing Pier C not D.
After that you just proceed to your gate and arrive hassile free as a domestic passenger in the US.
Unfortunately full CBP facilities will not be up and running until the new year. They want to bring it in step by step to deal with any teething problems that may arise with any new facility. They will start with what they have already which is Immigration but not Customs so flights will not be arriving as domestic flights until sometime in early 2011.
FANRAILUK
yes you can clear immigration and eventually customs even if you are transiting in DUB from another city. However, the flight from Cardiff connects with EI109 to JFK and there are no CBP immigration facilities provided for EI109 at the moment.